One of architectures of computer systems (information processing apparatuses) is that plural CPUs (Central Processing Unit) are mutually communicatively connected through buses. For example, such architecture is employed in a shared memory system, in which each CPU is connected with a memory and each memory is shared with the CPUs.
[Patent Document 1]                Japanese Laid-Open Patent Publication No. 2001-229080        
[Patent Document 2]                Japanese Laid-open Patent Publication No. H10-313330        
[Patent Document 3]                Japanese Laid-Open Patent Publication No. 2006-107071        